Pulse generation circuit



Y Jan. 6, 1948'. B, M OLIVER 2,433,863

PULSE GENERATION CIRCUIT Filed May 13, 1943 2 Sheets-Sheet l /Nl/E N TOR E? M. OUVER VVVVV ATTORNEK Jan. 6, 194s.`

B. M. OLIVER PULSE GENERATION CIRCUIT File'd May 13, 1943 2 Sheets-Sheet '2 l/vur vaLraG: ro russ v2 [curo/"r aus or rse v2 v'oLrAc: l

jpurf cu/mfn/r or ruse V2 curorf am.: of Tune v4 ,nur mmc: ar ruuw aum/r vamos no was: vs iw) hun* maza: or ruse v5 curafr or Tus: vs co/vmol. Gmo :mames OFT/.15E v6 /CUTOFT BIAS 0F TUBE'W /NvE/vmn B. M. OLIVER @RWI Afro/Mfr Patented Jan. 6, 1948 PULSE GENERATION CIRCUIT Bernard M. Oliver, New York, N. Y., assgnor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York rApplication May 13, 1943, Serial No. 486,780

12 Claims. (Cl. 250-2-7) This invention relates to electric circuits and more specifically to pulse generation circuits.

It is an object of the present invention to provide a novel pulse generator. A more specic object is to provide apparatus for generating a sharp pulse occurring at a controllable period of time after an initiating pulse. Still another object is to provide novel apparatus for generating a nat-topped pulse of controllable time duration.

Other objects and features of the invention will be apparent from the following description.

In accordance with a specific embodiment of the present'invention, chosen by way of example for illustrative purposes, a tuned circuit of parallel-connected inductance and capacity members is shock-excited by a sharp pulse and the resultant wave is damped after a fraction (onefourth) of an oscillation cycle. The resultant pulse obtained across this antiresonant circuit is utilized to produce a rectangular or squaretopped pulse whose time duration is substantially equal to one-quarter period of the natural oscillation of said circuit, plus one-half the duration of the exciting pulse. The rectangular pulse can be used, for example, for blanking purposes in television cathode 'ray tubes, or it can be used as a blanking or a notch pulse in oscilloscope circuits or in radio object-locator (radar) systems. As the duration of the rectangular wave is a linear function of the period of the tuned circuit, variation of the tuning of this circuit, such as by varying the inductance or the capacitance thereof, will vary the length of this period. The pulse obtained across the antiresonant circuit has a much greater slope at its zero intercept than is the case in a wave produced by a resistance-capacity circuit. The duration of the pulse is therefore more accurately controllable in the circuit arrangement of the present invention.

The square-topped pulse is also utilized inaccordance with a further aspect of this invention to generate a second sharp pulse at its trailing edge which second pulse is preferably produced by shock-exciting with a voltage step function a second tuned circuit of series-connected inductance and capacity members and damping the resultant wave within a fraction of an oscillation cycle. The length of the output pulse can be varied by tuning the second tuned circuit. If desired, the original pulse used to shock-excite the first tuned circuit (or an amplified version thereof) can be applied to an output circuit along with the second sharp pulse.

The invention in its diierent aspects will be more readily understood by referring to the fol- 2 lowing description taken in connection with the accompanying drawings forming a part thereof in which:

Fig. 1 is a circuit diagram of a pulse generating arrangement in* accordance with the invention; and v Fig. 2 comprises various diagrammatic and graphical representations to aid in understanding and `explaining Vvthe invention.

Referring more specifically to the drawings, Fig. 1 shows, by way'ofexample to make clear the principles of operation of the present invention, a circuit arrangement for forming an echo pulse having an accurately controllable delay with respect to an initiating pulse, and also for generating a blanlzin'gv pulse (preferably of rectangular form) of controllable duration. The circuit shown in Fig. 1 comprises ten vacuum tubes designated VI to VIU, inclusive. Brieily stated, VI is an amplifier and phase inverting tube; V2, V3 and V4 form an arrangement for generating a flat-topped pulse (ordinarily called a square-topped pulse) starting substantially at the commencement of the initiating pulse and ending a controllablel period of time later; V5 is an amplier, phase inverter, and clipper for the square-topped Wave; VB, V'I and V8 form an arrangement for utilizing the square-topped wave to generate a sharp pulse commencing substantially at the ending of said square-topped wave, the duration of the sharp or echo pulse being controllable; and V9 and VID are amplifiers, phase inverters and clippers for the pulse outputs of tubes V2 and V8. (A pulse simultaneous with the initiating pulse is developed in the screen circuit of V2.)

The initiating pulse, which can be generated by a multivibrator, or by any other means for producing sharp pulses, is applied to the tube VI from an input coaxial cable I0 terminated by a resistance II. The tube VI includes an anode I2, a cathode I3, agcontrol grid I4, a screen grid I5, and a suppressor grid I6. The resistance II is connected between the control grid I4 and the cathode I3, the cathode` being connected to ground. The suppressor grid I6 is connected to the cathode I3, while the screen grid I5 is connected through the voltage-dropping resistor I1 to the positive pole of a direct current source I9 of, for example, 300 volts, the negative pole of which is connected to ground. A by-pass condenser I8 is connected between the screen grid I5 and ground. The anode I2 is connected through the resistor 22, inductance 23, and the resistor 24 to the positive pole of the source I9, the comand the anti-sing resistor 21 (to prevent parar.v sitic oscillations) to the control grid 32 of the tube V2 which also comprises an anode 33, aj

lar in function to members 22, 23, 24, and in the anode circuit of tube VI. The anode 50 is also connected through a coupling condenser 53 and an anti-sing resistor 64 to the control grid l2 of the tube V5 which also includes an anode 1B, a cathode 1I, a screen grid 'I3 and a suppressor grid 1,4.. Biasfor the, tubeVE, is providedV by means ofthe condenser -'I5,.and .the resistor 'I6 shunted thereacross, these two elements .being connected between the cathode and ground.

The cathode 'll is also connected through a "bleedlerf"-resistor 'Il to the positive pole of the cathode 3l, a screen grid 3 3 anda suppressor grid 34. n means of a capacity member 35and a resistance member 36 shunted thereacross, these two mem- Bias for the grid 32 is provided byV source I9, Resistor v91 serves as a grid leak.

'Thesuppressor grid. T4 is connected to ground,

bers being connected between the. cathodenand ground. The bleeder resistor 31 is also connected between the cathode 3I and the positive Y pole of the source I9 to place the cathode 3| at a positive potentialeven when'no current-is flowing through the tube. Thesuppressor grid 34 -is connected to ground While the screen grid 3?y is connected through an anti-sing-resistor member 38'- and a resistory 35i-tothe positive-pole ofthe source I9, the common terminal Vof the resistors 33 and39 being connected through acapacity member 40-togroundi The members 39 and 49 serve as a filter and also provide lowfrequency equalization. The anode 39 is` connected throughresistor 4-I and the resistor 39to the -positive pole of thesource I9. Resistor |64serves as a grid leak.

Also connected to the anode 4Soi th-e tube V2 is the terminal AV ofthe condenser `lL-the terminal B of which isgconnected through the resistors v4 3 and k51cm/the control grid 52 of the tube V4 which also includes an; anodel5 a cathode 5I a, screen gridr53,and asuppressor grid 54. Connected betweenrthe terminal B oi the condenser 42 and ground is a tulledcircuit comprising a condenser 44. and a variable inductance member 45 connected in parallel. A-movable inner terminal 48 of the inductancemember i5-is connectedto ground. The diode tube V3 and the resistance member 43 .are alson connected in circuit between the point l" and 'ground- Preferably, the tube V3 comprises a cathode 52E-connected to ground and an anode 56v connectedto the resistor 43. The resistance of'ithe member 43 plus the resistance of. `the tube VSjpreferably equals the critical damping resistance ofthe inductancefcapacity tunedcircuit (which is equal to 1/2\/L/C, where L is the, inductance between terminal B and terminal 4B, andcis the capacity of the member 4.4.). The condenser i4-land the variable inductance 45 comprise .a .tuned .circuit TI which is shock-excited by output pulses from the` tube V2, while the tube V3 and the resistor 43 help dampout ,thebscillations caused by the shock excitation ofthistunedcircuit. Gridcurrent in the tube V4 may alsoserve to damp out these oscillations, as willbe pointedI out herei n ,V

afterin detail.

The cathodeSIand the suppressorgrid ,54. of

the tube V4 are preferably connected toground. Y

The resistor 5l is. connectedto the .control grid 52, Whilethe screen grid-.53, is connectedthrough a resistor 58. tothe positive terminalv of the source I9. The anode isconnected through a resistor 59 and inductancemember llandresstancel to the .positive terminal .of f the. source'. I 9; thecondenser 62 beingprovidedbetween the commenterminal of.- the members..(iIl` andy 6I. and ground. Members 59, 60, 6I, and 62 are respectively simiwhile the'screen. grid 'I3 is connected through the resistors 78 and 'I9 to the positive pole of the source. l9,'.they common terminal of resistors 'I8 and 'I 9 ..being connected through condenser 89 to ground. The functions o f members 'I9 and B are respectively similar to those of members 39. and 43 in the' anode c ircuitof 'tube V2.y The. anode 70 is connected through the resistors 3|. and 'i9 to the positive poleofthesource I9. The anode 'Iii can be coupled toiany suitable output circuit for utilizing a -blanking pulseby means oi, for example, a coupling condenser 82 and a resistor 93: This blanking pulse is a rectangular wave` in the negative vdirection extending from the commencement of the initiatingpulse v)from the input circuit I0 to the time the oscillation from the circuit Tl again exceeds the cut-.off bias of V4; It can be used, by way of'example, in a radio object-locator system to blank out all'Y echoes and noise in acomposite signal Wave between each transmitted pulse andta desired echo signal so the blanked-out portion will not be visible on the screen of a .cathode ray oscilloscope. It can be combined with the signal wave or it can be applied to thecontrol electrode of the oscilloscopeto cut ofi?Y the beamtherein periodically.

The rectangular wave in ,'the positive direction produced'at'the plateioi thetubeVdl is appliedto the control grid .92 of the tube V6 which also includesan anode 90,a cathode 9I a screen grid 93, and a suppressor grid 9 4. The cathode 9 I, and, the suppressor grid 94 are connected. to. ground through a resistor 951 having a condenser 9.6.. shunted across a portionthereof.` The resistor 97 is connected betweenthecontrolgrid '92 and. ground and servesasa. grid leak. The cathode9'l is also connected through ajbleeder resistorj98. to the positive polejof'the-sol110e I 9, ythe terminal ofthe resistor .98 remote frointhe cathodel being connected through. the.. bil-pass condenser. 99 to ground; The screen grd93 iscOnnected. through. a resistor Illlljto, the .positive pole. of thev source I Q ,While the anode yQ llis connectedthrough a resistor IDI to thesamepoint, The. anodeQIlis connectedto the terminal ,C of thecondenser m2,. the terminal D ofwhihis connected through a. resistor I UStothe.controlgrid I..I2 .o.f. the.tube V8; which also .includes an anode I.I ,a.cathode. I I I a screen grid I` I 3, and. asuppressor grid. II4.

Connected between the terminaljD.. and ,groundis wave setl up initheinductancef |94 linfa-manner- Y which will be described more fully below.

r The `cathode HI and the suppressor grid H4 ofthe tube V are connected to ground through a resistor H5 across a portion of which is connected a condenser H6. The resistor H5 and the condenser ||6 are used to provide bias for the tube V8. The cathode is also connected to the positive pole of the source I9 through a bleeder resistor ||1 and the resistor |20. The by-pass condenser H8 is connected between ground and the terminal ofthe resistor H1 remote from the cathode. The screen grid I3 is connected to the positive pole of the source |9 through a resistor H9 and the resistor |20, the common terminal of the resistors I9 and |20 being connected through the by-pass condenser H8 to ground. The plate H0 is connected through the resistor |2| to the positivepole of the source I9 and through a coupling condenser |22 to an intermediate terminal |23 of an input resistor |24 for the tube V9, the resistor being connected between ground and a contact member |1| of a switch |10 for a purpose which will be described hereinafter.

The tube V9 includes an anode |30, a cathode |3|, a control grid |32, a screen grid |33, and a suppressor grid |34. The upper terminal Vof the resistorY |24 is connected through an anti-sing resistor |35 to the control grid |32. The cathode |3| and the suppressor grid |34 are connected to ground and the screen grid is connected through the resistor |38 and the resistor |39 to the positive pole of the source I9, the common terminals of the resistors |38 and |39 being connected through a condenser |31 to ground. The plate |30 is connected through the resistor |40, inductance member |4| and resistor |42 to the positive pole of the source |3, the common terminal of the members |4| and |42 being connected through the condenser |43 to ground. The members |40, |4|, |42, and |43 have functions respectively similar to members 22, 23, 24, and 25 in the anode circuit of tube V|. The purpose of the tube V9 is to amplify a pulse produced in the output of the circuit of the tube V8 and also, as will be pointed out below, to amplify the negative pulses produced in the screen grid output circuit of the tube V2 vand to clip the tops of these pulses.

The anode |30 of the tube V9 is connected through a coupling condenser |44 and an antising resistor |45 to the control grid |52 of the tube VIO which also includes an anode |50, a cathode |5|, and a screen grid |53. A grid-leak resistor |54 is connected between the common terminal of the members |44 and |45 and ground. The cathode |5| is connected toground through the parallel-connected capacity member |55 and resistance member |53 which forms with the resistor |49 a potentiometer to provide bias for the grid |52 of such value that the tube V|0 acts to clip the bottoms of the positive pulses from V9. The screen grid |53 is connected through the resistor |51 to the positive pole of the source |9 and through the ley-pass condenser |58 to ground. The anode |50 is connected through the resistors |59 and |51 to the positive pole of the source |9 and through a coupling condenser |60 to one terminal |6| of an output circuit, the other terminal |62 of which is connected to ground. A resistance member |93 can be connected between the terminals |5| and |62, if desired.

If it is desired to have the original pulse, or rather an amplified and clipped version thereof, appear in the output circuit connected to the terminals ISI, |62, the switch is connected.`v

' amperes when the pulse drives the grid to zero tothe contact |1|, thus connecting the screen4 grid of the tube V2 through the blocking condenser |83 to the control grid |32 of the tube V9. The operation of the circuit shown in Fig. 1 is as follows, reference also being made to Fig. 2 which comprises various diagrammatic and graphical representations to aid in understanding and explaining the invention. The input pulse which, as shown in Fig. 2A, is a sharp negative pulse having, for example, a duration of about one microsecond is repeated four hundred times per second. It can be generated by any suitable means, such as by the well-known multivibrator arrangement or by any other well-known vacuum tube pulse generator, or by any suitable mechanical means. It can be, for example, a pulse sent from the transmitter of a radio object-locator or a pulse bearing a definite time relation, either before or after, to the transmitted pulse. This pulse is applied to the input circuit of tube Vl which acts as an' amplifier and phase inverter and produces a pulse, like that shown in Fig. 2B, which is applied to the input circuit of the tube V2. If the input pulse to the tube V| is of positive polarity (instead of negative) and of sufficient voltage, V|

may be dispensed with. The tube V2 is normally cut oi but it becomes conducting when the positive pulse shown in Fig. 2B is applied to its grid and passes a current of approximately 150 millibias. All but the direct component of the plate current of the tube V2 passes through the coupling condenser 42 to the tuned circuit comprising, for example, a 1,000 micromicrofarad condenser 44 which is shunted by a portion of the coil 4-5. The condenser 44 is charged by the plate current of V2 so that point B (and hence the control grid of tube V4) becomes negative with respect to ground. The plate current of the tube V2 is shown in Fig. 2C. The shape of the negative pulse produced by the charging of the condenser 44 is indicated by the portion |90 of the voltage Wave in Fig. 2D representing thepvoltage applied to the grid of the tube V4 in Fig. 2. Point Bris at substantially zero potential before the tube V2 becomes conducting and the terminal y A of the condenser 42 is at approximately 300 volts. When'the tube V2 becomes conducting, the

terminal A quickly drops to about volts potential and the terminal B is driven very quickly to a negative potential of about 200 volts. The condenser 44 starts to discharge through the inductance member 45 forming the portion |9| of the voltage wave shown in Fig. 2D. In the ab. sence of damping means this wave would tend to pass the zero axis and assume successively the Values indicated by the dotted line portion |92.'I

However, these oscillations are damped within approximately one-quarter of an oscillation cycle by means of the'resistance 43 and the diode V3 which becomes conducting as soon as the point B becomes slightly positive. As all of the energy producing the oscillations is absorbed in the circuit including the resistance 43 and the diode V3 (an-d the parallel connected circuit including resistance 51 and the control grid-cathode circuit of the tube V4), the oscillations are completely damped as shown by the full line portion |93 of the waves shown in Fig. 2D. If desired, the tube V3 and the resistance 43 can be omitted, the resistance 51 being made fairly low. In this latter situation, when the tube V4 starts to draw grid current because of the control grid 52 becoming:

thevvave shown in" Fig. 2D for a periodici` tirlfieI Which'isapproximately equal t'o about'oneuuarl-jv ter periodl of an" oscillation cycle plus oneflialf tleduration of'the'p'uls'e' from tubeVZ". 'This'is true'becausewith a symmetrical drivingpuls'e",`

the' resulting oscillat'ionis'of' the :forni- Where Ati-is thewidth of the driving pulse, and' t=0fatthe`start ofthe driving pulse. The first irlterce-ilit ofv the oscillation occurs Whenf 2 5- =`the` period `of 'the oscillation The-positive pulse |9'4t-hus prod-uced'on the' plate offthe tube Vity shovvn in Fig." 2E,isa'p'plied5to thev1 tube li-andcauses` this tube-to' conduct forVv a` p'eri'oolffofftirne corresponding to-the duration of the top of tl'ie pulse' |94 and to 'generate-`a`"useful= negati-ve blankingpulse across the terminals |34v 2Ff For exam-ple, this bla'nking-"ipulserv may; be-V u`sed to' cut ofi thelbeam of a cathode ray oscillog'raplji` -ior a 'period of time correspondingto the lengthof the' pulse |95 orit maybe added tothe received -vide'o signal in radio object locator'sys'- tems-to blankout all signals "between each translv`r mittedvrpulse and: a predetermined point in eachf train ofv received signals.- Th'efler'igth` of the blanking pulseV |95 can ybe IVariedby tuningthef' cilijziiitlY afsby varying the poSitioI-iof fthe inner cilcon'nection- 43; The length'of th'ef-delayi terval represented by lthe lpuls'e" |95 isa'` linear' This period in' turn ispr'oportinal totlie'siiuar'ey rct of the inductance of themernber 45` forniingi part ofv 'this' tuned circuit; Thisinductance iis p'roportionaltothe square of the number-'of turns* comprising the coil 45.- Accordin'gly, A the length" of `the delayinterval is a' linearffu'n'ction of the number ofv turnsincluded in this coil. Obviously, other'Ways-'of varying the tuningfof fthecircuitf TIV can* be utilized such asi-making@thecondenser' 44 "vari'able; for example,

TheI output 'puise from the l tubeffvaffiiown iii Fig'. 2E) is,l applied to the input circuit of 'the' tube Vinthe output circuit of'l whichis'the seL riesconnected tuned` circuit 'T2-'comprising he condenser |92Y and Vthe inductance member* IMS'V Thetube V|`conducts-a` pulse of plate current simmer' to that in the tube v5'. The-'control grid' coil' "l plate current' of Vl? ceas es,a positive tran- S' predice@- Duringthetime the'plaie. cur'- r'entf1 vvsj, thejcondenser" |02 is discharged. Y Y (It p uslyl had a; potential of v 300 volts across'v it" asthiejtube- Vli was cutfoi, thus/ placing the ter?,l ininal:` ('Jo'ffthel condenser I |l2 ata potential of about sooi volts;l tiie teiiiiinarl D being at sub- Staritiaiiy ground potential.) Whenthe grid of thetubeV|`is;l again driven negative,l the plate of tlieftiibe*Vti'sdiivenvpositive through the plate resistor IOLQcau'sing a' sinusoidal oscillation` of the turdicircuit which lastsi for one-half of a cyclefs'eelig. 2H), therernainder being damped by'ftletube V13. 'Ilf'ieI substantially 'undainpedoscil'l'ationsl which wouldf exist inthe absence of tubeVl are shovv'nin'v dotted linesin Fig; 2H'ai'1d theattiiaiwave'whicliis applied to thegifidtf thetube Viiiissliovvn as a full line: The rstl causes'a shortnegative pulse of plate voltage in thetube *V8* as shownfin*FigyrZL-developing a negative pulse on the :grid of-tubelV9, the magnitud "of Which 'depends' on the setting ofk theY potentorneterfrfesistor |'24 in the-input circuit of tll'ef'tub fV9t" At vthey same tirneithe' input pulsel after'so'me amplication bythe tubes VI and V2;

desiredv tok liavebotn pulses present in the out-y p'utfc'irrcuit' connectedl between the terminals IBI andl |62'. Both pulses'are ariiplifie'dandclipped` atbotliendsbytlie tubes V9l and 4Vlil to produce the output pulses, sa andato shown iti-Fig.V 2J provided* the' eclio 'gain control |23A` is set at thev fullgain"position.'V Ita reduced setting is', used' theHtDOfthecho'fwll'not be C1ppedand the outputaniplitude oithe echo may be reduced to any` desired value; including zero.y yTheV tuned "T2fin theoutput circuit orf tube' V6 de'- 'jtl'l'e output' pulsel length, that is, the' length" o'fth'e pulse 290' infFig. 2J. Thus, it will be appreciated vtl'ifat"'tliecircuit of this invention pr' ducesaroultputpulse AZilli; which can be veither tetti of which maybe p'rjeseiitin the output) cari be varied as" can"also"'the "duration Vof the vpulse 'Y 2991 'Obvioslyg the' amplitude of eitheror both; ofth "pilses'fcanbecontrolled as desired to make `rger than another or'boththeI same size.

lse 200" can :be used;Av for' example; to iniiviithmefererice*tothe pulse |99 by varying/the Obviously the invention; in any one of its several mi' whichdiler lfroimthose"described above' by Way Of example.'

condenser',` meansV "for applying to 'ectsniay be 'embodiedin'circuit arrange l "terminals re/spe'ctively connected "aisance 9 pulses of short duration compared with the natural period of oscillation of the circuit comprising said condenser and said inductance element, unil laterally conducting means in effective shunt to said condenser so poled that said charges cannot flow therethrough and that reverse charging of said condenser, from energy stored in said inductance element by the discharge of said condenser therethrough, is prevented, andmeans vforutilizing the potential set up across said inductance element to produce a rectangular potential ,Wave composed of pulses of substantially equal ampli= tude.

2. In combination, a condenser, a variable in- I.,

ductance element having terminals respectively connected to those of said condenser, means for applying to said condenser to charge it a series of potential pulses of short'duration compared with the natural period of oscillation of the circuit comprising said condenser and said variable inductance element, unilaterally conducting means in effective shunt to said condenser so poled that said charges cannot flow therethrough and that reverse charging of said condenser, from energy stored in said inductance element by the discharge of said condenser therethrough, is prevented, and means for utilizing the potential set up across said inductance element to produce a rectangular wave the duration of each pulse of which is equal to that of the other pulses thereof and Which is dependent upon the inductance of said variable inductance element.

3. In combination, means for producing a rectangular voltage pulse, a series-connected tuned circuit of inductance and capacity, said circuit having a natural period of oscillation which is long compared With the duration of said pulse, and means for applying said rectangular pulse to said tuned circuit to produce a sharp pulse of shorter duration than that of said rectangular pulse, said sharp pulse commencing substantially at the termination of said rectangular voltage pulse.

4. The combination of elements as in claim 3 in which means are provided for varying the tuning of said circuit.

5. In combination, a condenser, an inductance element having terminals respectively connected to those of said condenser, means for shock-exciting the circuit formed by said condenser and inductance element to produce an oscillation, means for damping said oscillation as soon as it rst reverses its direction, and means for utilizing the wave produced by said shock excitation and damping to form a second pulse substantially similar in shape to the pulse used to shock-excite the circuit but delayed with respect thereto.

6. In combination, a condenser, an inductance element having terminals respectively connected to those of said condenser, means for shock-exciting the tuned circuit formed by said condenser and inductance element to produce an oscillation, means for damping said oscillation as soon as it rst reverses its direction, and means for utilizing the wave produced by said excitation and damping to form a second pulse substantially similar in shape to the pulse used to shock-excite the circuit but delayed With respect thereto, the amount of the time delay being dependent upon the constants of said tuned circuit.

7. In combination, a rst tuned circuit of inductance and capacity, means for shock-exciting said circuit, means for damping and shaping the oscillation initiated by said shock excitation after a fraction of an oscillation cycle to produce a Y Vl Vsquare-topped pulse for each shock excitation, a second tuned circuit of inductance and capacity, means for utilizing each pulse produced by the shock excitation of said first tuned circuit to shock excite the second tuned circuit, means for damping substantially completely oscillations tending to be formed at the leading edge of said square-topped pulse and for damping all of the oscillations `started at the trailing edge of said square-topped pulse except for a one-half cycle 'voltage pulse, and means for utilizing said lastme'ntioned pulse.

8. Thecombination of elements as in claim 'I and being further characterized in that said second tuned circuit has a natural period of oscillation which is shorter than that of said first tuned circuit. l Y

' 9. In combination, a spacelcurrent device having an anode, a cathode and a control element, means for biasing said control element with respect yto said. cathode so that said device is normally'cut off, a capacity element, an inductance element, means for connecting said capacity elementv and said inductance element in a series circuit including the anode-cathode path of said space current device, unilaterally conducting means connected across said inductance element and being so poled that it conducts when the potential of the terminal of the inductance element connected to the capacity element is lower than the potential of the other terminal of the inductance element, means for applying a substantially rectangular positive pulse to the cathodecontrol element circuit of said device to make said device conducting for the duration of said pulse, and means for utilizing the resultant single voltage pulse appearing across said inductance element starting substantially simultaneously with the trailing edge of said rectangular positive pulse.

10. The combination of elements as in claim 9 in which said last-mentioned means includes means for producing a square-topped voltage pulse.

11. In combination, means for producing a rst series of pulses, and means for forming a second series of pulses under control of the pulses in said rst series each delayed by a definite amount from the corresponding pulse in the first series, said last-mentioned means comprising a rst tuned circuit of inductance and capacity members, means for shock exciting said circuit under control of each of the pulses of said rst series to quickly charge said capacity member and thereby set up an oscillation in said tuned circuit, means for damping said oscillation in approximately one fourth of an oscillation cycle and thereby forming in response to each pulse in said iirst series a negative voltage pulse across said condenser, means for clipping the lower portion of each of said negative pulses and for inverting the phase thereof to form a series of positivel square-topped pulses each starting substantially with the leading edge of a pulse in said first series and terminating after a period of time equal to said definite amount, said period being determined by the width of said pulse in the first series and the time constant of said tuned circuit, a second tuned circuit comprising inductance and capacity members, means under control of each of said positive square-topped pulses for starting oscillations at the time of occurrence of the leading and trailing edges thereof, means for dampleading edges and all of the oscillations at said trailing edges ,except fer thefirst pnsitire half yale 0i each 0f them, and means, for elipp, iig each ,Of Said positive half cyeles, ,te prediiee 'ssi tepped'pulse forming one of thenulees ef second series. I`12- Means under Ceritlel ,0i e iirstv short .Yeltaee Pulse ier generating@ Second 'pulse at the' termination of a desired delayperiod beginning with the application of said first pulse to' said means, comprising meansA for utilizing said contioi pulse to produce a relatively long rectangular pulse and means for utilizing the trailing edge of ,s aidlog Pulse t0,v generate et third pulse 'eempreiiig a tuned circuit irieludingiheeres relatioaa'ea- Dacity element; 'an' 'iridu'etaiiee element' and "a SQuree 0f direct potential, Said' eiiefiiitv having a natural period which is" small 'compared with the duration o f saidY long' puise, arid 'eeritrel means for discharging '.Saidfeeiidenser wider Qontrol. of theleading edge oflseid 1ere puise comprising a unilateraliy'eenduetine deyiee' feenneeted. arOSS the terminals Qi .saidindnetanee element poled in the direction te conduct 'current frein Said. .Condenser ,during Said discharge,

$099101 means eausing said condenser to charge again when said trailing edge of said long pulse isf applied to ,said control means to set up ya ptntial 'pulse across said inductance element.

' BERNARD M. OLIVER.

EEFEnENCEs CITED The following references are of record in the 111e of this, patent:

STATES PATENTS Number Name Date V2,063,025 Blur'nlein Dec. 8, 1936 l -2,139,432 Andrieu Dec. 6, 1938 2,181,309 Andrieu k Nov. 28, 1939 2,226,706 Cavveinr Dec. r31, 1940 2,256,336 BeattyA Sept. 16, 1941 2,113,214 Luck Apr. 5, 1938 2,153,202 Nichols Apr. 4, 1939 2,035,402 Vance June 29, 1937 2,188,653 Faudell et al. Jan. 30, 1940 2,244,003 Eagleseld et a1 June 3, 1941 2,408,061 Grieg Sept. 24, 1946 

